Downhole oil and gas production operations, and particularly those in multi-stage horizontal wells, require the stimulation and production of one or more zones of a hydrocarbon bearing formation. In many cases this is done by running a liner or casing string downhole, in which the casing string comprises one or more downhole tools, including but not limited to perforating devices, ported sleeves or collars, at spaced intervals along the wellbore. The location of the downhole tools is commonly set to align with the formation zones to be stimulated or produced. The tools must be manipulated in order to be opened or closed as required. In some instances, this is achieved by running a bottom hole assembly, also known as an intervention tool, down through the casing string, locating the downhole tool to be manipulated and manipulating the tool by any number of means including use of mechanical force on the intervention tool, or by hydraulic pressure.
The bottom hole assembly (BHA), or intervention tool, also known by any number of other names, is typically run on a tubing string that can be coil tubing or other tubing. The intervention tool is sent down inside the casing string for the purposes of locating inside and interacting with the downhole tool adjacent the formation zone to be treated or produced. Once located near or inside the downhole tool, the intervention tool typically engages against the downhole tool or against the casing near the downhole tool, and then the intervention tool is either mechanically manipulated or hydraulic pressure is used to manipulate the downhole tool as required to stimulate the oil-bearing formation, or to produce hydrocarbons from the formation. After treatment, it may also be desirable to again manipulate the downhole tool. In many cases, it is also desirable to locate and set an intervention tool in a casing string or a section of blank pipe.
A key goal in using an intervention tool is to accurately locate the intervention tool inside the downhole tool or inside section of casing or blank pipe before going through the process of setting the intervention tool and trying to manipulate any downhole tools. Since there can be miles and miles of casing string with any number of downhole tools and lengths of blank pipe along it, this can be difficult.
Furthermore, due to reaction time commonly seen in coil tubing deployment, there is a tendency for the tubing on which the intervention tool is run downhole to travel downhole even after it has been located in the desired downhole tool. This extra travel causes the intervention tool to ‘jump’ out of its proper location in the downhole tool.
In some prior art, intervention tools use drag blocks and locator blocks to locate the intervention tool in the downhole tool. However, in many of these cases, extra length is required to account for coil tubing travel, leading to larger, less flexible sleeves and downhole tools. These have also been proven less successful in operation. Also, this type of prior art system does not ensure that any slips and packers on the intervention tool won't set before the locator blocks are located.
Other locating means that have been used in the past include locating dogs, latching mechanisms or by estimating the location of the downhole tool in the wellbore and feeding a predetermined length of deployment string to reach the frac sleeve.
There is therefore still a need for intervention tool and downhole tool systems that can positively locate an intervention tool inside a downhole tool or inside casing string, and for systems that ensures that slips and packing elements cannot be set before locating.